From the bench to the bedside: Infrared, Raman, NMR and Brewster spectroscopies, and the cause and cure for dry eye

9th Global Ophthalmology SummitMarch 15-16, 2017 London, UK

Dry eye affects over six million people in the United States. Tears become more unstable with age and meibomian gland dysfunction
(MGD). Changes in the composition, and structure of a thin film of lipid on the surface of tears called the ‘tear film lipid layer’
(TFLL) may cause tears to become more unstable. In this study NMR spectroscopy was used to measure TFLL composition. Infrared,
Raman and Brewster angle spectroscopies were used to measure the structure of the TFLL. Langmuir trough technology was used
to measure TFLL rheology. Several abnormalities in the TFLL composition were identified that may contribute to TF instability
including terpenoids, saturation, protein and cholesteryl esters. When terpenoid levels in TFLL are low as in MGD, the TF is unstable
and patients have the signs and symptoms of dry eye. When terpenoids are restored with azithromycin treatment, TF stability is
restored and patients no longer have the signs and symptoms of dry eye. A more saturated TFLL contributed to TF stability. The
TFLL phase transition temperature and hydrocarbon chain decrease with increasing age. It is reasonable that stronger lipid-lipid
interactions could stabilize the tear film since these interactions must be broken for tear breakup to occur. Meibum is fluid enough
to be expressed from the meibomian glands and becomes more ordered (viscous) on the surface of the eye. A stiff ordered molecular
arrangement results in a more elastic TFLL in which molecules are able to rearrange during the compression and expansion of a blink.